Channel selection for uplink access

ABSTRACT

Systems, methods, and instrumentalities are disclosed for a wireless transmit/receive unit (WTRU) to transmit uplink information. The WTRU may have information such as data or control information to transmit to a network. The (WTRU) may request a common enhanced dedicated channel (E-DCH) resource from the network. The WTRU may receive an indication from the network to fallback using a random access channel, e.g. a Release 99 Random Access Channel (R99 RACH), a Release 99 Physical Random Access Channel (R99 PRACH), etc. The indication may be received via an acquisition indicator (E-AI). The indication may be a value of the E-AI. The WTRU may determine whether a condition is met. The WTRU may transmit the uplink information over the R99 PRACH if the condition is met.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/301,759, filed on Jun. 11, 2014, which is a continuation of U.S.patent application Ser. No. 13/570,647, filed Aug. 9, 2012, which issuedas U.S. Pat. No. 8,792,447 on Jul. 29, 2014; which claims the benefit ofU.S. Provisional Patent Application No. 61/522,504, filed Aug. 11, 2011,U.S. Provisional Patent Application No. 61/555,201, filed Nov. 3, 2011,and U.S. Provisional Patent Application No. 61/589,760, filed Jan. 23,2012, the contents of which are hereby incorporated by reference herein.

BACKGROUND

Mobile networks have experienced continuous increases in data trafficdue in part to the introduction of new mobile services and applications.Such traffic may be characterized by its high level of burstiness and/orsmall packet sizes. In Universal Mobile Telecommunications Systems(UMTS), mobile devices experiencing varying traffic demands may bemaintained in non-fully connected states during periods of low activity,such as, but not limited to CELL_FACH or CELL_PCH. The non-fullyconnected states may help to provide a user experience that is closer to“always-on connectivity,” while maintaining low battery consumption.

SUMMARY

Systems, methods, and instrumentalities are disclosed for a wirelesstransmit/receive unit (WTRU) to transmit uplink information. The WTRUmay have information such as data or control information to transmit toa network. The (WTRU) may request a common enhanced dedicated channel(E-DCH) resource from the network. The WTRU may receive an indicationfrom the network to fallback using a random access channel, e.g. aRelease 99 Random Access Channel (R99 RACH), a Release 99 PhysicalRandom Access Channel (R99 PRACH), etc. The indication may be receivedvia an acquisition indicator (E-AI). The indication may be a value ofthe E-AI. The WTRU may determine whether a condition is met. The WTRUmay transmit the uplink information over the R99 PRACH if the conditionis met.

The condition may be met if one or more of the following is established:the channel for transmission is capable of being mapped to the R99 RACH;the channel for transmission may be configured with a fixed Radio LinkControl (RLC) Protocol Data Unit (PDU) size; or the channel fortransmission belongs to a list of channels that is predefined in theWTRU, whereby the list may include one or more of a common controlchannel (CCCH) or a dedicated control channel (DCCH). If the conditionis not met, the WTRU may back off from accessing the network, ignore theindication from the network to fallback to the R99 PRACH, wait for atime, and attempt to access the network.

DESCRIPTION OF THE DRAWINGS

FIG. 1A is a system diagram of an example communications system in whichone or more disclosed embodiments may be implemented.

FIG. 1B is a system diagram of an example wireless transmit/receive unit(WTRU) that may be used within the communications system illustrated inFIG. 1A.

FIG. 1C is a system diagram of an example radio access network and anexample core network that may be used within the communications systemillustrated in FIG. 1A.

FIG. 1D is a system diagram of another example radio access network andanother example core network that may be used within the communicationssystem illustrated in FIG. 1A.

FIG. 1E is a system diagram of another example radio access network andanother example core network that may be used within the communicationssystem illustrated in FIG. 1A.

FIG. 2 illustrates an exemplary fallback.

DETAILED DESCRIPTION

A detailed description of illustrative embodiments will now be describedwith reference to the various Figures. Although this descriptionprovides a detailed example of possible implementations, it should benoted that the details are intended to be exemplary and in no way limitthe scope of the application.

FIG. 1A is a diagram of an example communications system 100 in whichone or more disclosed embodiments may be implemented. The communicationssystem 100 may be a multiple access system that provides content, suchas voice, data, video, messaging, broadcast, etc., to multiple wirelessusers. The communications system 100 may enable multiple wireless usersto access such content through the sharing of system resources,including wireless bandwidth. For example, the communications systems100 may employ one or more channel access methods, such as code divisionmultiple access (CDMA), time division multiple access (TDMA), frequencydivision multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrierFDMA (SC-FDMA), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, and/or 102 d (whichgenerally or collectively may be referred to as WTRU 102), a radioaccess network (RAN) 103/104/105, a core network 106/107/109, a publicswitched telephone network (PSTN) 108, the Internet 110, and othernetworks 112, though it will be appreciated that the disclosedembodiments contemplate any number of WTRUs, base stations, networks,and/or network elements. Each of the WTRUs 102 a, 102 b, 102 c, 102 dmay be any type of device configured to operate and/or communicate in awireless environment. By way of example, the WTRUs 102 a, 102 b, 102 c,102 d may be configured to transmit and/or receive wireless signals andmay include user equipment (UE), a mobile station, a fixed or mobilesubscriber unit, a pager, a cellular telephone, a personal digitalassistant (PDA), a smartphone, a laptop, a netbook, a personal computer,a wireless sensor, consumer electronics, and the like.

The communications systems 100 may also include a base station 114 a anda base station 114 b. Each of the base stations 114 a, 114 b may be anytype of device configured to wirelessly interface with at least one ofthe WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to one or morecommunication networks, such as the core network 106/107/109, theInternet 110, and/or the networks 112. By way of example, the basestations 114 a, 114 b may be a base transceiver station (BTS), a Node-B,an eNode B, a Home Node B, a Home eNode B, a site controller, an accesspoint (AP), a wireless router, and the like. While the base stations 114a, 114 b are each depicted as a single element, it will be appreciatedthat the base stations 114 a, 114 b may include any number ofinterconnected base stations and/or network elements.

The base station 114 a may be part of the RAN 103/104/105, which mayalso include other base stations and/or network elements (not shown),such as a base station controller (BSC), a radio network controller(RNC), relay nodes, etc. The base station 114 a and/or the base station114 b may be configured to transmit and/or receive wireless signalswithin a particular geographic region, which may be referred to as acell (not shown). The cell may further be divided into cell sectors. Forexample, the cell associated with the base station 114 a may be dividedinto three sectors. Thus, in one embodiment, the base station 114 a mayinclude three transceivers, i.e., one for each sector of the cell. Inanother embodiment, the base station 114 a may employ multiple-inputmultiple output (MIMO) technology and, therefore, may utilize multipletransceivers for each sector of the cell.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 115/116/117,which may be any suitable wireless communication link (e.g., radiofrequency (RF), microwave, infrared (IR), ultraviolet (UV), visiblelight, etc.). The air interface 115/116/117 may be established using anysuitable radio access technology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 103/104/105 and the WTRUs 102a, 102 b, 102 c may implement a radio technology such as UniversalMobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA),which may establish the air interface 115/116/117 using wideband CDMA(WCDMA). WCDMA may include communication protocols such as High-SpeedPacket Access (HSPA) and/or Evolved HSPA (HSPA+). HSPA may includeHigh-Speed Downlink Packet Access (HSDPA) and/or High-Speed UplinkPacket Access (HSUPA).

In another embodiment, the base station 114 a and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Evolved UMTSTerrestrial Radio Access (E-UTRA), which may establish the air interface115/116/117 using Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.16 (i.e.,Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000,CDMA2000 1x, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), InterimStandard 95 (IS-95), Interim Standard 856 (IS-856), Global System forMobile communications (GSM), Enhanced Data rates for GSM Evolution(EDGE), GSM EDGE (GERAN), and the like.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, and the like. In oneembodiment, the base station 114 b and the WTRUs 102 c, 102 d mayimplement a radio technology such as IEEE 802.11 to establish a wirelesslocal area network (WLAN). In another embodiment, the base station 114 band the WTRUs 102 c, 102 d may implement a radio technology such as IEEE802.15 to establish a wireless personal area network (WPAN). In yetanother embodiment, the base station 114 b and the WTRUs 102 c, 102 dmay utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, etc.) to establish a picocell or femtocell. As shown in FIG. 1A,the base station 114 b may have a direct connection to the Internet 110.Thus, the base station 114 b may not be required to access the Internet110 via the core network 106/107/109.

The RAN 103/104/105 may be in communication with the core network106/107/109, which may be any type of network configured to providevoice, data, applications, and/or voice over internet protocol (VoIP)services to one or more of the WTRUs 102 a, 102 b, 102 c, 102 d. Forexample, the core network 106/107/109 may provide call control, billingservices, mobile location-based services, pre-paid calling, Internetconnectivity, video distribution, etc., and/or perform high-levelsecurity functions, such as user authentication. Although not shown inFIG. 1A, it will be appreciated that the RAN 103/104/105 and/or the corenetwork 106/107/109 may be in direct or indirect communication withother RANs that employ the same RAT as the RAN 103/104/105 or adifferent RAT. For example, in addition to being connected to the RAN103/104/105, which may be utilizing an E-UTRA radio technology, the corenetwork 106/107/109 may also be in communication with another RAN (notshown) employing a GSM radio technology.

The core network 106/107/109 may also serve as a gateway for the WTRUs102 a, 102 b, 102 c, 102 d to access the PSTN 108, the Internet 110,and/or other networks 112. The PSTN 108 may include circuit-switchedtelephone networks that provide plain old telephone service (POTS). TheInternet 110 may include a global system of interconnected computernetworks and devices that use common communication protocols, such asthe transmission control protocol (TCP), user datagram protocol (UDP)and the internet protocol (IP) in the TCP/IP internet protocol suite.The networks 112 may include wired or wireless communications networksowned and/or operated by other service providers. For example, thenetworks 112 may include another core network connected to one or moreRANs, which may employ the same RAT as the RAN 103/104/105 or adifferent RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities, i.e., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks. For example, the WTRU 102 c shown in FIG. 1A may be configured tocommunicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram of an example WTRU 102. As shown in FIG. 1B,the WTRU 102 may include a processor 118, a transceiver 120, atransmit/receive element 122, a speaker/microphone 124, a keypad 126, adisplay/touchpad 128, non-removable memory 130, removable memory 132, apower source 134, a global positioning system (GPS) chipset 136, andother peripherals 138. It will be appreciated that the WTRU 102 mayinclude any sub-combination of the foregoing elements while remainingconsistent with an embodiment. Also, embodiments contemplate that thebase stations 114 a and 114 b, and/or the nodes that base stations 114 aand 114 b may represent, such as but not limited to transceiver station(BTS), a Node-B, a site controller, an access point (AP), a home node-B,an evolved home node-B (eNodeB), a home evolved node-B (HeNB), a homeevolved node-B gateway, and proxy nodes, among others, may include someor all of the elements depicted in FIG. 1B and described herein.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Array (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 115/116/117. For example, in one embodiment,the transmit/receive element 122 may be an antenna configured totransmit and/or receive RF signals. In another embodiment, thetransmit/receive element 122 may be an emitter/detector configured totransmit and/or receive IR, UV, or visible light signals, for example.In yet another embodiment, the transmit/receive element 122 may beconfigured to transmit and receive both RF and light signals. It will beappreciated that the transmit/receive element 122 may be configured totransmit and/or receive any combination of wireless signals.

In addition, although the transmit/receive element 122 is depicted inFIG. 1B as a single element, the WTRU 102 may include any number oftransmit/receive elements 122. More specifically, the WTRU 102 mayemploy MIMO technology. Thus, in one embodiment, the WTRU 102 mayinclude two or more transmit/receive elements 122 (e.g., multipleantennas) for transmitting and receiving wireless signals over the airinterface 115/116/117.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as UTRA and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 130 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 115/116/117from a base station (e.g., base stations 114 a, 114 b) and/or determineits location based on the timing of the signals being received from twoor more nearby base stations. It will be appreciated that the WTRU 102may acquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, and the like.

FIG. 1C is a system diagram of the RAN 103 and the core network 106according to an embodiment. As noted above, the RAN 103 may employ aUTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102 cover the air interface 115. The RAN 103 may also be in communicationwith the core network 106. As shown in FIG. 1C, the RAN 103 may includeNode-Bs 140 a, 140 b, 140 c, which may each include one or moretransceivers for communicating with the WTRUs 102 a, 102 b, 102 c overthe air interface 115. The Node-Bs 140 a, 140 b, 140 c may each beassociated with a particular cell (not shown) within the RAN 103. TheRAN 103 may also include RNCs 142 a, 142 b. It will be appreciated thatthe RAN 103 may include any number of Node-Bs and RNCs while remainingconsistent with an embodiment.

As shown in FIG. 1C, the Node-Bs 140 a, 140 b may be in communicationwith the RNC 142 a. Additionally, the Node-B 140 c may be incommunication with the RNC 142 b. The Node-Bs 140 a, 140 b, 140 c maycommunicate with the respective RNCs 142 a, 142 b via an Iub interface.The RNCs 142 a, 142 b may be in communication with one another via anIur interface. Each of the RNCs 142 a, 142 b may be configured tocontrol the respective Node-Bs 140 a, 140 b, 140 c to which it isconnected. In addition, each of the RNCs 142 a, 142 b may be configuredto carry out or support other functionality, such as outer loop powercontrol, load control, admission control, packet scheduling, handovercontrol, macrodiversity, security functions, data encryption, and thelike.

The core network 106 shown in FIG. 1C may include a media gateway (MGW)144, a mobile switching center (MSC) 146, a serving GPRS support node(SGSN) 148, and/or a gateway GPRS support node (GGSN) 150. While each ofthe foregoing elements are depicted as part of the core network 106, itwill be appreciated that any one of these elements may be owned and/oroperated by an entity other than the core network operator.

The RNC 142 a in the RAN 103 may be connected to the MSC 146 in the corenetwork 106 via an IuCS interface. The MSC 146 may be connected to theMGW 144. The MSC 146 and the MGW 144 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices.

The RNC 142 a in the RAN 103 may also be connected to the SGSN 148 inthe core network 106 via an IuPS interface. The SGSN 148 may beconnected to the GGSN 150. The SGSN 148 and the GGSN 150 may provide theWTRUs 102 a, 102 b, 102 c with access to packet-switched networks, suchas the Internet 110, to facilitate communications between and the WTRUs102 a, 102 b, 102 c and IP-enabled devices.

As noted above, the core network 106 may also be connected to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

FIG. 1D is a system diagram of the RAN 104 and the core network 107according to an embodiment. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102c over the air interface 116. The RAN 104 may also be in communicationwith the core network 107.

The RAN 104 may include eNode-Bs 160 a, 160 b, 160 c, though it will beappreciated that the RAN 104 may include any number of eNode-Bs whileremaining consistent with an embodiment. The eNode-Bs 160 a, 160 b, 160c may each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the eNode-Bs 160 a, 160 b, 160 c may implement MIMO technology. Thus,the eNode-B 160 a, for example, may use multiple antennas to transmitwireless signals to, and receive wireless signals from, the WTRU 102 a.

Each of the eNode-Bs 160 a, 160 b, 160 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the uplink and/or downlink, and the like. As shown in FIG. 1D, theeNode-Bs 160 a, 160 b, 160 c may communicate with one another over an X2interface.

The core network 107 shown in FIG. 1D may include a mobility managementgateway (MME) 162, a serving gateway 164, and a packet data network(PDN) gateway 166. While each of the foregoing elements are depicted aspart of the core network 107, it will be appreciated that any one ofthese elements may be owned and/or operated by an entity other than thecore network operator.

The MME 162 may be connected to each of the eNode-Bs 160 a, 160 b, 160 cin the RAN 104 via an S1 interface and may serve as a control node. Forexample, the MME 162 may be responsible for authenticating users of theWTRUs 102 a, 102 b, 102 c, bearer activation/deactivation, selecting aparticular serving gateway during an initial attach of the WTRUs 102 a,102 b, 102 c, and the like. The MME 162 may also provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as GSM or WCDMA.

The serving gateway 164 may be connected to each of the eNode-Bs 160 a,160 b, 160 c in the RAN 104 via the S1 interface. The serving gateway164 may generally route and forward user data packets to/from the WTRUs102 a, 102 b, 102 c. The serving gateway 164 may also perform otherfunctions, such as anchoring user planes during inter-eNode B handovers,triggering paging when downlink data is available for the WTRUs 102 a,102 b, 102 c, managing and storing contexts of the WTRUs 102 a, 102 b,102 c, and the like.

The serving gateway 164 may also be connected to the PDN gateway 166,which may provide the WTRUs 102 a, 102 b, 102 c with access topacket-switched networks, such as the Internet 110, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and IP-enableddevices.

The core network 107 may facilitate communications with other networks.For example, the core network 107 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices. For example, the corenetwork 107 may include, or may communicate with, an IP gateway (e.g.,an IP multimedia subsystem (IMS) server) that serves as an interfacebetween the core network 107 and the PSTN 108. In addition, the corenetwork 107 may provide the WTRUs 102 a, 102 b, 102 c with access to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

FIG. 1E is a system diagram of the RAN 105 and the core network 109according to an embodiment. The RAN 105 may be an access service network(ASN) that employs IEEE 802.16 radio technology to communicate with theWTRUs 102 a, 102 b, 102 c over the air interface 117. As will be furtherdiscussed below, the communication links between the differentfunctional entities of the WTRUs 102 a, 102 b, 102 c, the RAN 105, andthe core network 109 may be defined as reference points.

As shown in FIG. 1E, the RAN 105 may include base stations 180 a, 180 b,180 c, and an ASN gateway 182, though it will be appreciated that theRAN 105 may include any number of base stations and ASN gateways whileremaining consistent with an embodiment. The base stations 180 a, 180 b,180 c may each be associated with a particular cell (not shown) in theRAN 105 and may each include one or more transceivers for communicatingwith the WTRUs 102 a, 102 b, 102 c over the air interface 117. In oneembodiment, the base stations 180 a, 180 b, 180 c may implement MIMOtechnology. Thus, the base station 180 a, for example, may use multipleantennas to transmit wireless signals to, and receive wireless signalsfrom, the WTRU 102 a. The base stations 180 a, 180 b, 180 c may alsoprovide mobility management functions, such as handoff triggering,tunnel establishment, radio resource management, traffic classification,quality of service (QoS) policy enforcement, and the like. The ASNgateway 182 may serve as a traffic aggregation point and may beresponsible for paging, caching of subscriber profiles, routing to thecore network 109, and the like.

The air interface 117 between the WTRUs 102 a, 102 b, 102 c and the RAN105 may be defined as an R1 reference point that implements the IEEE802.16 specification. In addition, each of the WTRUs 102 a, 102 b, 102 cmay establish a logical interface (not shown) with the core network 109.The logical interface between the WTRUs 102 a, 102 b, 102 c and the corenetwork 109 may be defined as an R2 reference point, which may be usedfor authentication, authorization, IP host configuration management,and/or mobility management.

The communication link between each of the base stations 180 a, 180 b,180 c may be defined as an R8 reference point that includes protocolsfor facilitating WTRU handovers and the transfer of data between basestations. The communication link between the base stations 180 a, 180 b,180 c and the ASN gateway 182 may be defined as an R6 reference point.The R6 reference point may include protocols for facilitating mobilitymanagement based on mobility events associated with each of the WTRUs102 a, 102 b, 102 c.

As shown in FIG. 1E, the RAN 105 may be connected to the core network109. The communication link between the RAN 105 and the core network 109may defined as an R3 reference point that includes protocols forfacilitating data transfer and mobility management capabilities, forexample. The core network 109 may include a mobile IP home agent(MIP-HA) 184, an authentication, authorization, accounting (AAA) server186, and a gateway 188. While each of the foregoing elements aredepicted as part of the core network 109, it will be appreciated thatany one of these elements may be owned and/or operated by an entityother than the core network operator.

The MIP-HA may be responsible for IP address management, and may enablethe WTRUs 102 a, 102 b, 102 c to roam between different ASNs and/ordifferent core networks. The MIP-HA 184 may provide the WTRUs 102 a, 102b, 102 c with access to packet-switched networks, such as the Internet110, to facilitate communications between the WTRUs 102 a, 102 b, 102 cand IP-enabled devices. The AAA server 186 may be responsible for userauthentication and for supporting user services. The gateway 188 mayfacilitate interworking with other networks. For example, the gateway188 may provide the WTRUs 102 a, 102 b, 102 c with access tocircuit-switched networks, such as the PSTN 108, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and traditionalland-line communications devices. In addition, the gateway 188 mayprovide the WTRUs 102 a, 102 b, 102 c with access to the networks 112,which may include other wired or wireless networks that are owned and/oroperated by other service providers.

Although not shown in FIG. 1E, it will be appreciated that the RAN 105may be connected to other ASNs and the core network 109 may be connectedto other core networks. The communication link between the RAN 105 theother ASNs may be defined as an R4 reference point, which may includeprotocols for coordinating the mobility of the WTRUs 102 a, 102 b, 102 cbetween the RAN 105 and the other ASNs. The communication link betweenthe core network 109 and the other core networks may be defined as an R5reference, which may include protocols for facilitating interworkingbetween home core networks and visited core networks.

Systems, methods, and instrumentalities are disclosed for a wirelesstransmit/receive unit (WTRU) to transmit uplink information. The WTRUmay have information such as data or control information to transmit toa network. The (WTRU) may request a common enhanced dedicated channel(E-DCH) resource from the network. The WTRU may receive an indicationfrom the network to fallback using a random access channel, e.g. aRelease 99 Random Access Channel (R99 RACH), a Release 99 PhysicalRandom Access Channel (R99 PRACH), etc. The indication may be receivedvia an acquisition indicator (E-AI). The indication may be a value ofthe E-AI. The WTRU may determine whether a condition is met. The WTRUmay transmit the uplink information over the R99 PRACH if the conditionis met.

The condition may be met if one or more of the following is established:the channel for transmission is capable of being mapped to the R99 RACH;the channel for transmission may be configured with a fixed Radio LinkControl (RLC) Protocol Data Unit (PDU) size; or the channel fortransmission belongs to a list of channels that is predefined in theWTRU, whereby the list may include one or more of a common controlchannel (CCCH) or a dedicated control channel (DCCH). If the conditionis not met, the WTRU may back off from accessing the network, ignore theindication from the network to fallback to the R99 PRACH, wait for atime, and attempt to access the network.

A wireless transmit/receive unit (WTRU) may be in an idle state or aconnected state. Based on the WTRU mobility and activity while in theconnected state, a universal terrestrial radio access network (UTRAN)may direct the WTRU to transition between a number of sub-states, whichmay include one or more of the following: CELL_PCH, URA_PCH, CELL_FACH,or CELL_DCH states. User plane communication between the WTRU and theUTRAN may be possible while in CELL_FACH and CELL_DCH states. TheCELL_DCH state may be characterized by dedicated channels in uplink anddownlink. On the WTRU side, the CELL_DCH state may correspond tocontinuous transmission and/or reception and may be demanding on userpower requirements. The CELL_FACH state may not use dedicated channelsand, thus may allow better power consumption at the expense of a loweruplink and downlink throughput.

Uplink communication may be achieved through a random access channel(RACH) mapped to a physical random access channel (PRACH). The RACH maybe a contention-based channel. A power ramp-up procedure may be used toacquire a channel and/or to adjust transmit power. An RACH may be ashared channel used for an initial access to obtain dedicated resourcesand/or to transmit small amount of data. There may be collisions betweentwo or more WTRUs trying to access the channel simultaneously.

The RACH procedure may have a channel acquisition stage, which may use aslotted-ALOHA mechanism, followed by an RACH message transmission stage.For example, a WTRU that wants to access a channel may randomly select asignature and transmit an RACH preamble to a Node B during a randomlyselected access slot at a certain transmit power level. If the Node Bdetects the signature and if an associated resource is free, the Node Bmay transmit a positive acknowledgement (ACK) on an acquisitionindicator channel (AICH). After receiving an acquisition indicator (AI)(e.g., ACK), on the AICH, the WTRU may transmit an RACH message. If theassociated resource is unavailable, the Node B may respond with anegative acknowledgement (NACK) on the AICH. This may trigger a back-offmechanism at the WTRU. The WTRU may start a back-off timer (e.g., Tbo1).After expiry of the timer, a preamble ramping cycle count may beincremented and the procedure may start again. This may restart the RACHprocedure at a later random time. If the RACH preamble from the WTRU isnot detected at the Node B, an AI may not be transmitted on the AICH. Ifthe WTRU fails to receive an AI after transmission of the RACH preamble,the WTRU may try again in a subsequent access slot with a randomlychosen signature and/or a higher transmit power. This may continue up toa maximum number of times.

The signature may be chosen randomly from a list of available signaturesand/or the RACH access procedure may be anonymous. The Node B may notknow which WTRU is accessing the channel until the Node B decodes theRACH message. When two or more WTRUs happen to choose the same signaturein the same access slot and one of them is detected by the Node B, theNode B may transmit an ACK. The WTRUs may interpret this as a havingacquired the channel and may access the channel simultaneously totransmit RACH messages. This may cause a collision on the RACH messages.When a collision occurs, the RACH messages may not be decoded correctly.Collisions may be difficult to detect and/or incur additional delays.

The RACH procedure may be divided between the medium access control(MAC) layer and the physical layer. The physical layer may control, forexample, the preamble transmission, signature selection, access slotselection, and/or preamble transmit power. The MAC layer may control,for example, the interpretation of the AICH response (for example, ACK,NACK, and/or no response), and/or the start of the physical layerprocedure. Transmission failure and successful completion of the MACprocedure may be indicated individually for each logical channel, forexample, using primitives (such as but not limited to, CMAC-STATUS-Indfor the radio resource control (RRC) and/or MAC-STATUS-Ind for the radiolink control (RLC)).

The uplink transmission mechanism in CELL_FACH state may be modified bycombining the RACH channel acquisition stage with an enhanced dedicatedchannel (E-DCH). The procedure may be referred to as enhanced uplink forCELL_FACH and IDLE mode. The Node B may select an E-DCH resource from aset of common E-DCH resources that may be shared amongst the WTRUs. TheNode B may respond to a WTRU channel access request by assigning one ofthese resources. The WTRU may then start transmission over the assignedE-DCH transport channel.

One channel selection scheme may be that common E-DCH capable WTRUs mayuse common E-DCH when operating in a cell that supports common E-DCH.Otherwise, the WTRU may use the Release 99 RACH. In another channelselection scheme, the use of both R99 RACH and common E-DCH may be usedby WTRUs in cells that support both channels. Common E-DCH capable WTRUsmay “fallback” to R99 RACH for UL transmission if, for example, commonE-DCH resources are congested and/or simply because the nature of the ULtransmission is better suited to the R99 RACH channel.

Criteria that may be used for selection of the UL channel may bedisclosed. This may include, but is not limited to, whether the WTRU orthe RAN should make the channel selection. The selection criteria may becoordinated between WTRU and RAN, e.g., to ensure that, for example,there is no confusion between nodes while ensuring backwardscompatibility for WTRUs that are not capable of fallback to R99 RACH.

A fallback to R99 RACH may result in transmission of data over a R99PRACH from a logical channel configured with flexible a RLC PDUconfiguration. For example, the R99 RACH may not support MACsegmentation and/or may transmit a limited set of Transport Block Sizes(TBSs). As a result, RLC PDUs created for transmission over common E-DCHmay not be compatible for transmission over R99 RACH.

Implementations described herein may relate to selection between commonE-DCH and R99 RACH channels for UL transmission in Idle mode, URA_PCH,CELL_PCH and/or CELL_FACH states. As referred to herein, “fallback toR99 RACH” may refer to the use of the R99 RACH channel for transmissionof UL control information and/or data by a WTRU that may be capable oftransmitting over common E-DCH while operating in a cell that may becapable of reception over both R99 RACH and common E-DCH. As referred toherein, the term “non-DCH states” may be used to describe a state wherethe WTRU may not be fully connected to the RAN (for example, does nothave a set of dedicated resources for DL reception and UL transmission).For example, with specific reference to UMTS networks, the term “non-DCHstates” may refer to one or more of the following states: IDLE Mode,URA_PCH State, CELL_PCH State, or CELL_FACH State. Other types of accessnetworks may utilize similar non-DCH states to which the implementationsdescribed herein may be applicable.

A WTRU may determine when to perform R99 RACH access. Example triggersare described herein which may be used individually or in anycombination. For example, the triggers may be used in conjunction withthe triggering conditions and/or selection criteria described inPCT/US08/80971, entitled SELECTING TRANSMISSION PARAMETERS FORCONTENTION-BASED ACCESS IN WIRELESS SYSTEMS, filed Oct. 23, 2008, whichis incorporated herein by reference.

A common E-DCH access failure may refer to one or more of the following:A NACK on the extended acquisition indicators (E-AI), a number ofconsecutive NACKs, a number of NACKs over a period of time; a NACK onthe acquisition indicator channel (AICH) if no E-AI is configured; acollision resolution failure; no response on the AI (e.g., within acertain time duration); or a maximum number of preamble attempts isreached.

A WTRU may use one or more of buffer content, network signaling orcongestion level to determine whether to fallback to R99 RACH. Forexample, if a common E-DCH access fails, if the network redirects to theWRTU to use R99 RACH, and/or if the WRTU is capable of R99 RACHfallback, then the WTRU may determine whether it can use R99 RACH, e.g.,if one or more of conditions are met. A condition may be that a buffersize is below a threshold (which may be configurable or predefined). Forexample, WTRUs with larger buffer size may re-try a common E-DCH accessprocedures rather than fallback to R99 RACH. After a predefined numberof re-tries, the WTRU may determine that it may be appropriate tofallback to R99 RACH. A condition may be that the total UL data thatneeds to be transmitted may fit into a R99 RACH TTI according to theallowed TBS and power in the WTRU. A condition may be that the ULlogical channel or logical channel type belongs to a list of logicalchannels that may be mapped and/or that may be allowed to fallback toPRACH. For example, the WTRU may be allowed to fallback and/or transmitUL information from the list of logical channels over the R99 RACH. TheWTRU may be allowed to fallback and/or transmit UL information forcertain logical channels from the list of logical channels over the R99RACH. The list of which logical channels may be allowed to betransmitted over R99 RACH may be configured, for example, by the networkvia RRC signaling and/or predefined in the WTRU. For example, apredefined set of logical channels may be configured in the WTRU and/orthe network may configure the WTRU with which logical channel type(s)the WTRU may fallback to R99 RACH. Such logical channels may be of thesignaling type that may comprise higher priority data and/or lowerpayloads than data traffic channels. An example of such a channel typemay be CCCH logical channel type. When configured and/or predefined withCCCH, the WTRU may determine it may fallback to R99 PRACH if the UL datato transmit is of CCCH type. An example of such a channel type may beDCCH. For example, if the network redirects the WTRU to fallback to R99RACH (e.g., the E-AI value and/or the E-DCH resource index correspond tothe fallback stored in the WTRU), the WTRU may check if the UL datatransmission comprises data from the predefined and/or configured list(e.g., if the data is from CCCH logical channel types or DCCH), and thenthe WTRU may fallback for transmission to R99 RACH. If the logicalchannel for UL transmission is not one that is allowed by the configuredlogical channel types (e.g., DTCH), then the WTRU may not perform RACHfallback. A condition may be that a dedicated E-RNTI may or may not beconfigured for that WTRU. Other conditions may also trigger the fallbackuse of R99 RACH.

A dedicated RRC signal and/or message may be used to configure the WTRUto use R99 RACH for UL transmission. For example, the message maycorrespond to a RRC message configuring the WTRU to use R99 RACH. Theconfiguration may be performed using, for example, a Cell Update Confirmmessage, a RRC reconfiguration message, and/or a System informationmessage. For example, an Information Element (IE) may be broadcastedindicating to WTRUs capable of fallback to R99 RACH to use R99 RACH forUL transmission. The indication to fallback to R99 RACH may includeadditional criteria that may be used by a WTRU to determine if it shouldfallback to R99 RACH. For example, the fallback to R99 RACH may apply toa group of WTRUs for which a particular identifier and/or WRTU identity(e.g., E-RNTI) lies within a predefined and/or signaled range of values.Fallback to R99 RACH may apply for certain types of traffic (e.g., CCCH)and/or to WTRUs operating in certain states (e.g., IDLE mode andURA_PCH).

The RRC signaling may indicate the time duration for which a fallback toR99 RACH may be performed after the reception of that message. Forexample, a timer may be reset upon receipt of the message. Once thetimer expires, the WTRU may start using common E-DCH again. An explicitmessage may be used to explicitly indicate to the WTRU to stopperforming fallback to R99 RACH. The time duration for which a fallbackto R99 RACH may be performed may be signaled using system information.

A Radio Link Protocol (RLC) configuration may be used when determiningto fallback to R99 RACH. For example, a R99 RACH may not be used withflexible RLC PDU configuration, as the transport block supported by RACHmay be fixed and/or the MAC used for R99 access may not havesegmentation capabilities. The RLC PDU configuration may be taken intoaccount when determining the fallback decision/triggers. The WTRU mayuse R99 RACH if one or more criteria related to the RLC may besatisfied, e.g., as described herein. The criteria may be that thelogical channel which has UL data to transmit may be configured withfixed RLC PDU. The criteria may be whether the logical channel may beconfigured with TM or UM RLC. The criteria may be whether the RLC PDUsalready created in the RLC entity may fit in the allowed TB sizes of theR99 RACH. The criteria may be that there may be no RLC PDUs in theretransmission buffer. The criteria may be that there may be no RLC PDUsalready created in the RLC entity (e.g., there are not RLC PDUs alreadypre-generated but not yet transmitted, and/or there are not RLC PDUs tobe retransmitted). For example, if RLC PDUs are already created, thesize of the RLC PDUs on the logical channel may correspond to an allowedRLC PDU size, as broadcasted in the system information and/or providedto the WTRU via an RRC message. If there are RLC PDUs already created,the RLC PDUs may be smaller than or equal to the allowed RLC PDU sizethat may be broadcasted as part of the RACH system information. Forexample, the RLC PDUs that are smaller may be any size or a size that isa function of the allowed size (e.g. a fraction).

The criteria described herein may be used by the WTRU to determine oneor more of the following. The criteria described herein may be used bythe WTRU to determine whether to autonomously fallback. The criteria maybe used by the WTRU to determine whether to fallback after a networkindication (e.g., if the network indicates fallback and the criteria isnot met, the WTRU may ignore the network indication). The criteriadescribed herein may be used by the WTRU to determine whether it ispermitted to fallback and perform a R99 RACH selection. The criteriadescribed herein may be used by the WTRU to determine whether to use R99RACH. The criteria described herein may be used by the WTRU to determinethe above and indicate to the network that the criteria may be met(e.g., the WTRU may fallback to R99 RACH).

For example, the network may determine channel control. As referred tohereafter, a channel or resource selection in a non-DCH state mayinclude one or more of the following channel selections: R99 RACH,Common E-DCH, Common E-DCH with 2 ms TTI, or Common E-DCH with 10 msTTI.

A channel or resource selection may also be used interchangeably withTTI selection and/or transport channel selection. For example, TTIselection may correspond to a selection of a common E-DCH with 2 ms or10 ms TTI. Transport channel selection may correspond to a selectionbetween RACH and common E-DCH. Implementations may be described hereinwhere the network may dynamically control the TTI and/or transportchannel selection.

The WTRU may perform an initial TTI and/or transport channel selectionand may indicate a TTI and/or transport channel selection preference tothe network. The network may dynamically control the TTI and/ortransport channel selection.

The WTRU may perform a preamble transmission based on, for example, acommon E-DCH and/or WTRU capability. The network may dynamically controlthe UL resources that the WTRU may use for UL transmission.

The WTRU may perform an initial TTI and/or transport channel selectionbased on a number of criteria and preferred resource access. Forexample, upon selecting a TTI and/or transport channel, the WTRU mayinitiate an UL RACH procedure by selecting a preamble from a group ofpreambles that correspond to the selection of the WTRU.

For example, the WTRU may determine to use, that it is allowed to use,and/or that it may prefer to use a R99 RACH resource if one or more ofthe following conditions are satisfied/established. The conditions mayinclude, but are not limited to, one or more of the following: the WTRUis be capable of fallback to R99 RACH; the network is capable of R99RACH fallback; the buffer size of the WTRU is below a threshold; theWTRU is transmitting data corresponding to a logical channel that is ina list of allowed/configured logical channels for which R99 RACH may beallowed (e.g., CCCH); a common E-DCH access has failed; or any of theconditions related to a fallback to R99 RACH are satisfied. For example,the WTRU may determine that there are no already created RLC PDUs in theRLC entity. For example, the WTRU may determine that there are no RLCPDUs already created in the RLC entity (e.g., in the retransmissionbuffer or in the RLC created but not yet transmitted) that maycorrespond to a size different than the allowed broadcasted RLC PDUsize.

The WTRU may perform TTI selection (e.g., select a preamble from a setof 2 ms TTI resources or 10 ms TTI resources) if one or more of thefollowing conditions are met. The conditions may include, but are notlimited to, one or more of the following: the WTRU is capable ofconcurrent 2 ms and 10 ms TTI operation (e.g., the WTRU may choosebetween 2 ms and 10 ms TTI for UL common E-DCH access); the network iscapable of concurrent 2 ms and 10 ms TTI operation; the WTRU istransmitting data corresponding to a logical channel that is in a listof allowed/configured logical channels for which concurrent 2 ms and 10ms TTI operation may be allowed; the WTRU may determine to use 2 ms or10 ms TTI resources based on select conditions (such as, but not limitedto WTRU power headroom); the buffer size in the WTRU may also be used toselect the TTI; or the buffer size may be used in addition to, forexample, the power margin and/or WTRU headroom criteria (e.g., if thepower margin may be above a threshold and/or the buffer occupancy may beabove a threshold, the WTRU may select the 2 ms TTI; and if the buffermay be below a threshold, the WTRU may select the 10 ms TTI).

Based on TTI selection and/or the transport channel selection, the WTRUmay determine the preamble to use for UL preamble transmission.

If the WTRU determines to fallback (e.g., select R99 RACH), the WTRU mayautonomously fallback to R99 RACH resources (e.g., PRACH systeminformation) and may perform the R99 procedure to determine the preamblefrom the set of allowed preambles for R99 RACH (e.g., the legacy R99RACH).

For example, if the WTRU determines to select and/or determine that itis allowed to use RACH to transmit data, it may chose a preamble from aset of preamble reserved to distinguish WTRUs that may use and/or thatmay prefer to use R99 RACH over common E-DCH.

Preamble groups may be reserved and may be used by WTRUs that may selecta different TTI for common E-DCH. For example, a group of preambles maybe reserved for WTRUs that prefer to use a TTI different than the TTIused for the common E-DCH resources (e.g., legacy common E-DCHresources). For example, two groups of preambles may be reserved for 2ms and 10 ms TTIs respectively for WTRUs that may select the TTI.

At least a set of preamble resources may be reserved and/or may bebroadcasted/signaled for WTRUs that can make use of transmission oneither R99 RACH or common E-DCH and/or for WTRUs that can perform TTIselection on common E-DCH. A set of preamble resources may correspond toone or more of the following parameters: a set of preamble signatures; aseparate scrambling code; or a set of reserved access slots.

For transport channel selection, preamble resources may be reserved tobe used by WTRUs that may be allowed to and/or prefer to perform R99RACH transmission, e.g., according to any of the selection criteriadiscussed herein, which may be referred to as “R99 fallback PRACHresources.” If the selection criteria as described herein is met and/orthe WTRU determines that it is allowed to and/or prefers to use R99RACH, then the WTRU may select a preamble signature and/or a scramblingcode from the R99 fallback PRACH resources and/or may initiate preambletransmission. For example, the scrambling code may be specific to R99fallback resources and/or it may be common to the common E-DCHresources. The selection, for example as described herein, may becarried out at the beginning of the PRACH procedure and/or at a preambleretransmission.

For TTI selection, a preamble resource may be reserved according to oneor more of the following. Preamble resources (e.g., one or more newpreamble resources may be configured) may be reserved for one or moreWTRUs that may support 2 ms and 10 ms TTI selection. Preamble resourcesfor 2 ms and/or 10 ms TTI selection may be signaled. For example,preamble resources (e.g., new preamble resources) may bereserved/signaled for WTRUs that support a TTI other than the TTIsignaled for the common E-DCH WTRUs (e.g., legacy common E-DCH WTRUs).For example, if the common E-DCH resources (e.g., legacy common E-DCHresources) have a TTI configuration of 10 ms, preamble resources (e.g.,new preamble resources) may be reserved for WTRUs that select 2 ms TTIaccording to the criteria above.

A set of preamble resources may correspond to one or more of: a set ofpreamble signatures; a separate scrambling code; or a set of reservedaccess slots. Preamble resources may be reserved according to one ormore of the following. One scrambling code may be used for R99 fallbackcapable WRTUs and one scrambling code for common E-DCH WRTUs. Thepreamble signatures within the scrambling code used for common E-DCH maybe divided between common E-DCH WRTUs (e.g., legacy common E-DCH WRTUs)and concurrent 2 ms/10 ms TTI WRTUs, where preamble signatures may bereserved for 2 ms TTI access and 10 ms TTI access. For example, onescrambling code may be used for concurrent 2 ms/10 ms TTI capable WRTUsand a another scrambling code may be used for the fallback R99 capableWRTUs. For example, one scrambling code may be used for concurrent 2ms/10 ms TTI capable WRTUs and fallback R99 WRTUs. The preamblesignatures within this scrambling code may be divided according to oneor more of the following. Preamble signatures may be divided between 2ms and 10 ms common E-DCH access. The set of preamble resources may besignaled for 2 ms and a another set may be signaled for the 10 ms commonE-DCH, for example, in addition to the legacy common E-DCH preambleresource set. For example, if the WRTU uses any of these signaturesand/or scrambling code, it may mean that the WRTU is R99 fallbackcapable. Preamble signatures may not be divided further for R99 RACHfallback capable WRTUs. For example, preamble signatures may be dividedbetween 2 ms and 10 ms common E-DCH access and R99 RACH fallback capableWRTUs. For example, a WRTU may choose to use a preamble signature fromthe R99 RACH fallback set of resources if the conditions described beloware met.

A WTRU may determine which set of reserved preambles to use for initialpreamble access according to different criteria and/or preferred channelaccess. For example, the WRTU may determine to select a preamble from aR99 RACH fallback set of resources if one or more of conditions are met.The conditions may include one or more of the following: that the WTRUis fallback to R99 RACH capable; that a common E-DCH access has failed;that the buffer size of the WTRU is below a threshold; that the WTRU istransmitting data corresponding to a logical channel that is in a listof allowed/configured logical channels for which R99 RACH may be allowed(e.g., CCCH and/or DCCH); or any of the conditions described herein fora fallback to R99 RACH are met.

Based on the UL resource selection (e.g., R99 RACH or 2 ms and/or 10 mscommon E-DCH), the WTRU may determine which PRACH resources to use forpreamble transmission.

A WRTU may determine whether to select a preamble from a set ofconcurrent 2 ms and 10 ms TTI resources if one or more of the followingconditions are met: the WRTU is capable of concurrent 2 ms and 10 ms TTIoperation (e.g., it may chose between 2 ms and 10 ms TTI for UL commonE-DCH access); the WRTU is transmitting data corresponding to a logicalchannel that is in a list of allowed/configured logical channels forwhich R99 RACH is possible (e.g., CCCH); or the WRTU determines withinthe 2 ms and 10 ms TTI set, the group from which resources are chosen.

A WTRU may determine to transmit and/or that it prefers to transmit onR99 RACH. The WTRU may select a preamble from the R99 RACH fallbackPRACH resources. If the WTRU determines that it prefers to use commonE-DCH, the WTRU may determine the TTI to use based on the TTI selectioncriteria described above. The WTRU may select a preamble from the PRACHresources corresponding to a chosen TTI value from the reserved group ofpreambles.

If PRACH resources are broadcasted for a TTI configuration differentthan the common E-DCH (e.g., legacy common E-DCH), then the WTRU maychose a preamble from that set of PRACH resources, for example, if theWTRU selects a different TTI than the common E-DCH (e.g., legacy commonE-DCH). Otherwise, the WTRU may select a preamble from the PRACHresources signaled for the common E-DCH resources (e.g., legacy commonE-DCH resources).

This may allow the network to determine that WTRUs making such accessmay be UL channel selection capable, such as but not limited to fallbackto R99 RACH capable and/or concurrent 2 ms/10 ms TTI capable and/or havepotentially met the criteria above and/or expressed a choice of ULchannel. The network may use this information to determine whatresources to allocate to the WTRU (e.g., RACH or Common E-DCH, and,within common E-DCH it may determine whether to use 2 ms TTI or 10 msTTI).

The WTRU may use one or more of the UL channel resources in a flexibleway controlled by the network. For example, a set of preamble resourcesmay be reserved for a group of WTRUs that may make use of transmissionon R99 RACH and/or common E-DCH.

Using the pool of selected preamble resources, for example, the WTRU maystart performing the preamble ramp-up phase according to procedures(e.g., legacy procedures) and may wait for an explicit indication todetermine which set of resources to use. Even though the preambleresources may be split and/or grouped for different UL accesses, thephysical resources used for UL access (e.g., the PRACH and/or the CommonE-DCH resources) may be split from resources (e.g., legacy resources),or, the same resources may be used. For example, a default associationbetween the preamble group and UL resources may be defined.

The determination of which resources to use for UL access may be basedon a set of rules and/or on explicit signaling by the network. Thedecision making process in the WTRU may be according to one or more ofthe following. A reserved preamble group may have a default associatedset of UL resources. If the WRTU chooses the preamble from the dedicatedR99 fallback RACH preamble set, the default set of resources associatedwith this preamble set may be a set of R99 RACH resources. The R99 RACHresources may be associated to a set of PRACH resources (e.g., legacyPRACH resources) (e.g., the first PRACH configuration if more than oneis available), or a set of specific R99 fallback PRACH info may bedefined and used. For example, the preamble group associated with a 2 msTTI or a 10 ms TTI common E-DCH may have as a default set a set of thecommon E-DCH resource set configured with 2 ms or 10 ms respectively.The 2 ms preamble set and 10 ms preamble set may have as a default setthe same common pool of E-DCH resources. The common E-DCH resources maybe used with any TTI value. This common E-DCH resource set maycorrespond to the legacy set of Common E-DCH resources and/or to a setof common E-DCH resources (e.g., new set of common E-DCH resources). Ifthe legacy common E-DCH resource is chosen, the default set may be thecommon E-DCH configuration (e.g., legacy common E-DCH configuration). Ifthe WTRU selects the common E-DCH set, then the network may not redirectthe WTRU to another UL resource, for example, because it may not beaware that the WTRU supports such UL resource selection.

An AICH may be used to acknowledge the use of a default set of resourcesand the E-AI may be used to explicitly redirect the WRTU to a differentset of resources. After choosing a preamble from a preamble group, theWRTU may transmit the preamble and may monitor the AICH. If an ACK onthe AICH is received, this may be interpreted as an acknowledgment thatthe defined default set of resources associated to the selected preamblemay be used. If a preamble from R99 fallback PRACH resources is chosenand/or an ACK was received on the AICH and/or the default resources arethe R99 RACH resources, then the WTRU may initiate the R99 RACH messagepart transmission using the default physical set of resourcessignaled/broadcasted on the SIB. The scrambling code and/or signaturesequences of the selected preamble may be used to determine thechannelization code and/or perform UL transmission. For example, if a 2ms TTI preamble is transmitted and an ACK is received, the WTRU mayinitiate common E-DCH transmission using the 2 ms TTI configuration anduse the common E-DCH resource corresponding to the resource.

A NACK on the AICH may indicate a failure to access the defaultassociated resources (e.g., if the default chosen may be a resourceother than the legacy common E-DCH). The WTRU, after a failure to accessthe default resource, may retry again after a back off timer. The WTRUmay use a preamble chosen from a different group of resources, or, fromthe same set of resources. For example, if initial access was with R99fallback RACH and a NACK was received, the WTRU may retry again after aback-off time expires using the common E-DCH. The WTRU may attempt onthe other non-default resources if failure to the default resources wasdetected for N attempts, where N may be network configurable and/or maycorrespond to the maximum number of preamble transmissions. This may beapplicable if no Extended Acquisition Indicator (EAI) is configured.This mechanism may be applicable for some WTRUs and for some specificdefault resources (e.g., for R99 RACH). This mechanism may be applied tothe scenario where a NACK is received on the EAI. This may be applied bythe WTRU if a NACK may be received on the EAI, and/or if a NACK may bereceived for N attempts. For example, an EAI may be a value thatcorresponds to a combination of a signaled signature and modulationsignal.

The reception of a NACK may signal to the WTRU that it may startmonitoring the EAI for, for example, an explicit resource indication onthe other non-default resource set and/or an index to a set of resourcessignaled on the default set. An index signaled over the EAI maycorrespond to an index to a non-default set. A non-default set maycorrespond to another UL channel and/or another TTI value. If the R99RACH is the default set, then the non-default set may correspond to acommon E-DCH set (e.g., the legacy common E-DCH set with one TTIconfiguration or a common E-DCH set which may have any TTIconfiguration). An assumption may be made that a R99 fallback compatibleWTRU also supports TTI selection. The E-AI may signal an index which maybe used in conjunction with the selected R99 fallback preamble todetermine which common E-DCH index to use.

If the default set is a 2 ms TTI set, then the EAI may correspond to anindex for the 10 ms TTI set. If the default set is a common E-DCH set,then an EAI may be used to signal a fallback to R99 RACH. This mayindicate a preamble index to use for UL access and/or a PRACH index. TheEAI may be used to signal what UL channel to use according to any of themethods described herein.

The reception of a NACK may trigger the WTRU to start monitoring theEAI. The EAI may indicate what resource the WRTU may use. For example,one or more EAI values may be used to indicate one UL resource. Theremaining EAI values may be used to indicate another UL resource. Forexample, for transport channel selection, at least one or a subset of ULresources may be used to indicate the use of R99 PRACH (e.g., an indexto a signature sequence, s) and the remaining subset may be used toindicate a common E-DCH index. For example, at least one value of theEAI may be used and/or reserved to indicate that the WRTU should performa R99 RACH fallback and/or perform a R99 RACH access using signaledPRACH information. A reserved EAI value may be used by WRTUs thatperform access using a preamble from one of the group of preambles thatindicate support of R99 RACH access (e.g., either the R99 fallbackpreambles and/or the concurrent 2 ms/10 ms TTI preambles, for example,under the assumption that such WTRUs support R99 fallback). The EAIvalue corresponding to a fallback may be a predefined value (e.g., thesame value as used for NACK over the EAI or any new value). The reservedvalue may be configured and/or signaled to the WTRU. A value in the listof common E-DCH resources (e.g., a common E-DCH resource index) may bereserved for R99 RACH fallback indication. The reserved value may beconfigured via RRC signaling and/or predefined. The WTRU may receivewhich index and/or value that may correspond to a R99 fallback as partof the R99 fallback configuration information and/or the values may bepredefined. For example, if the received EAI value (e.g., signatureand/or modulation symbol) is equal to the configured and/or stored R99fallback value, then the WTRU may determine that it may fallback to R99RACH transmission, for example, if the criteria described herein aremet. For example, if the received and/or calculated E-DCH resource indexis equal to the configured and/or stored R99 fallback index, then theWTRU may perform R99 RACH transmission, for example, if the othercriteria described herein are met.

A subset of the EAI values (e.g., k) may be used to indicate an index toa set of 2 ms common E-DCH resources. Another subset of EAI values(e.g., l) may be used to indicate an index to a set of 10 ms TTIresources. For example, if 16 common E-DCH resources are used for 10 msTTI and 16 for 2 ms TTI, the WRTU may determine to use a 10 ms commonE-DCH resource if the indicated value received over the E-AI wouldcorrespond to a resource from 0-15 (e.g., 0 to k−1) and a 2 ms resourceif the index corresponds to a value of 16-31 (e.g., k to l+k−1). Thismay be achieved if the 2 ms and 10 ms TTI resources are maintained asone list, if the first x resources correspond to the 2 ms TTIconfiguration, and the remaining resources correspond to a 10 ms TTIconfiguration. The EAI may be used to signal a value that may be thenused to determine an index to the common E-DCH list. Based on the commonE-DCH index, the WRTU may determine if the associated resource has a 2ms or a 10 ms TTI configuration. If the index, for example, correspondsto a value between 0 and x−1, then the resource may be a 2 ms TTIresource, otherwise it may be a 10 ms TTI resource.

The EAI may be used to signal any of the UL channels and/or resources.The index determined after reception of the EAI may correspond to a R99PRACH, 2 ms TTI, or 10 ms TTI. A list of values may be reserved on theEAI to signal a R99 PRACH, a 2 ms TTI, and/or a 10 ms TTI. For example,one or more indexes may refer to 2 ms TTI (0 . . . x−1), one or moreindexes may refer to 10 ms TTI (x . . . x+y−1), and one or more indexesmay be used to indicate a fallback to a R99 PRACH for UL access, where xmay be the list of configured 2 ms TTI resources, y may be the list ofconfigured 10 ms common E-DCH resources, and the sum of the resources donot exceed a certain maximum number (e.g., 32).

For example, if the common E-DCH resources between the 2 ms TTI and the10 ms TTI configuration are split, then the default common E-DCH index,X, for a TTI configuration may correspond to X=Siglnd mod (N), where Nmay be the maximum number of common E-DCH resources configured with thecorresponding selected TTI. The default common E-DCH index X may bedetermined based on a WTRU's initial TTI selection (e.g., N maycorrespond to the maximum number of common E-DCH resources with theselected TTI).

The default X value may be dependent on whether an ACK on the AICH isreceived or whether an EAI is received. If an ACK is received, the valueX and the common E-DCH index to use may be determined as describedherein. If an EAI is received and the full EAI range of values is usedto signal any index to a common E-DCH list that includes both 2 ms TTIand 10 ms TTI, then the value X may be determined by X=Siglnd mod (N),where N may be the maximum common E-DCH resources for TTIconfigurations. If the E-AI values are split to signal different TTIconfigurations, then N may correspond to the maximum common E-DCHresources with a TTI configuration corresponding to the TTI associatedto the EAI value.

Siglnd may be the Nth PRACH preamble signature corresponding to the AIthat is configured available in the cell and corresponding to E-DCHtransmission for Enhanced Uplink in CELL_FACH state and IDLE mode forselected TTI configurations.

If an E-AI is used to signal an index to a common E-DCH resource, theWTRU may use the formula (X+EAI value) mod Y, where Y may be the totalnumber of common E-DCH resources (e.g., regardless of the TTIconfiguration). The WTRU may use the formula (X+EAI value) mod N, whereN may be the maximum number of common E-DCH resources with acorresponding TTI configuration. The corresponding TTI configuration maybe determined based on a default mapping and/or based on the value ofthe EAI (e.g., that may be reserved as described herein).

Two or more E-AIs may be configured to indicate an UL channel to use.The WRTU may monitor for two or more E-AIs (e.g., simultaneously).Depending on which EAI the resource index is received, the WRTU maydetermine which UL channel to use.

A list of R99 RACH resources and/or common E-DCH resources may besignaled and/or associated to the preamble set. The AI may be used toacknowledge the use of a resource associated to the index of thepreamble randomly selected (e.g., it may be either R99 RACH or commonE-DCH). The EAI may be used to signal an index. Based on this indexand/or the preamble selected, the WTRU may determine the index to theresource it may use.

A common E-DCH resource may be used with 2 ms TTI or 10 ms TTIconfiguration. The AI and/or the EAI may indicate to the WRTU which TTIit may use for the corresponding common E-DCH resource. The preamblegroup may be separated between the 2 ms TTI and 10 ms TTI, but thecommon E-DCH resource list may be one list and each resource may be usedwith any TTI configuration. The WRTU may determine what UL channel itwants to use (e.g., PRACH or common E-DCH). If the WTRU chooses a commonE-DCH, the WTRU may determine what TTI configuration it wants to use. Ifthe WTRU chooses a 2 ms TTI, then a preamble from the 2 ms TTI preamblegroup may be chosen. In order to determine whether it is allowed to usea 2 ms TTI or 10 ms TTI, one or more of the following techniques may beused. An ACK on the AICH may be used as an indication that the E-DCHresource associated with the chosen preamble and the TTI configurationcorresponding to the preamble group that should be used. A NACK on theAICH may be used as an indication that the WRTU should not use thechosen TTI (e.g., the TTI associated with the preamble group). The WRTUmay monitor the EAI to determine what resource it may use with the TTI(e.g., the new TTI). The NACK may be used as an indication that the WRTUmay monitor the EAI. The WRTU may not have determined what TTI it mayuse.

The EAI may be used to indicate to the WRTU what TTI it should use. Forexample, the reserved field of the AICH may be used to indicate whichTTI the WRTU should use. The response on the AICH (e.g., ACK/NACK) maybe used in combination with the reserved field to determine what TTI touse. The reserved field may be used to indicate two values or just onevalue (e.g., two values may be used to indicate what TTI value to use,and one value may used to indicate whether the WRTU should change thechosen TTI value). If an ACK is received on the AICH, the WRTU maydetermine to the use the associated common E-DCH index with a TTIconfiguration as indicated in the reserved field of the EAI. If an NACKis received on the AICH, the WRTU may determine to monitor an EAI (ifconfigured) for a resource indication. The TTI that the WRTU may use forthe signaled resource over the EAI may be the TTI as indicated on thereserved field with the NACK.

The network may control channel selection (e.g., TTI or transportchannel selection) for individual and/or groups of WTRUs. The networkmay control the fallback or use of R99 RACH for UL transmission. TheWTRU may wait for an indication to fallback to R99 RACH. The network maycontrol the common E-DCH channel type the WRTU should use, such as, butnot limited to, a 10 ms or a 2 ms common E-DCH channel. After triggeringa preamble transmission, the WTRU may wait for signaling to determinewhich UL channel to use, such as, but not limited to, to fallback or useR99 RACH, to use 2 ms TTI, and/or to use 10 ms TTI. For example, atleast one value in the E-AI may be reserved and/or used to signalfallback to R99 RACH, fall back to another TTI value for Common E-DCH,and/or to signal what TTI the WRTU should use for common E-DCH. Uponreception of this value over the E-AI, the WTRU may autonomouslyfallback to R99 RACH, may autonomously fallback to using another TTIvalue (e.g., other than the requested one), or may start using the TTIvalue indicated by the reserved value of the AICH and/or the E-AI in thecase of TTI selection. The reception of a NACK (e.g., on the E-AI if theE-AI is configured, or on the AI if no E-AI is configured) may alsoserve as signaling used to control the WRTU and indicate a fallback. Atleast one resource index and/or a set of resources in the list of commonE-DCH may be reserved for a specific UL channel (e.g., used for fallbackto R99 RACH or to use 2 ms TTI or 10 ms TTI). When a fallback to R99RACH capable WRTU and/or a WRTU that may be capable of changing TTIvalues for common E-DCH receives this resource allocation over the E-AI,the WTRU may select the indicated channel for transmission (e.g., R99RACH or a common E-DCH with the indicated TTI value). WTRUs (e.g.,legacy WTRUs) may use the resource indicated by the index as a commonE-DCH resource. For example, the reserved field of the AICH and/or theE-AICH may be used to indicate to the WTRU to fallback to R99 RACHand/or to select another TTI.

A secondary E-AICH code may be monitored by fallback to R99 RACH capableWRTUs and/or WRTUs capable of changing TTI values for common E-DCH. Thesecondary E-AICH may be configured by a network (e.g., by broadcastsignaling and/or via dedicated signaling). The network may be fallbackto R99 RACH capable and/or capable of changing the Common E-DCH TTI ULaccess. The secondary E-AI may be used to indicate a fallback to R99RACH and/or a common E-DCH TTI. The secondary E-AI may be used toindicate a preamble resource from the R99 PRACH resources that the WTRUmay use for its RACH access. The secondary E-AI may be further used toindicate a preamble and/or common E-DCH resource configured with a TTIand/or a common E-DCH resource index with a specific TTI.

In order for the WTRU to determine whether and when to monitor thesecondary E-AI, one or more criteria may be used. The criteria mayinclude, but are not limited to, that a UL channel selection capableWTRU (e.g., fallback to R99 RACH and/or common E-DCH with differentTTIs) may monitor the primary and secondary E-AICH. The reserved fieldin the AICH may be used to indicate to the WTRU to monitor the secondaryEAI. The reserved field of the AICH may be used to signal a value thatmay correspond to an indication that the WTRU should fallback to R99RACH and/or that it should change TTIs. The reserved field of the AICHmay be used to signal to the WTRU that it should monitor a EAI (e.g., asecondary E-AI) to potentially receive a resource assignment and/or anyother signal. Detection of NACK signaled on the primary E-AI may be usedas a criterion. Upon reception of a NACK on the E-AI and/or in the AI(e.g., if a primary EAI is not configured for legacy WTRUs), a ULchannel selection capable WTRU may start to monitor a secondary EAI. TheWTRU may start monitoring the EAI a certain time period after one of theconditions described herein are met.

The network may determine the capabilities of WTRUs by the use of one ormore (e.g., a set of) reserved preamble groups for R99 RACH capableWTRUs (e.g., as determined by the criteria described herein). Thenetwork may use any of the implementations described herein to indicateto a WTRU whether to fallback to R99 RACH or to common E-DCH.

A WTRU may perform transport channel selection. The WTRU may indicate apreference for resources. The WTRU may determine if the WTRU and thenetwork support transport channel selection and/or fallback to R99 RACH.The WTRU may determine if the criteria described herein are met. Forexample, the WTRU may determine if the buffer status is below or equalto a threshold. The WTRU may determine whether RLC PDUs are created andpresent in a retransmission buffer. If there are no RLC PDUs in thebuffer, the WTRU may determine if RLC PDUs with a size different and/orgreater than the allowed RLC PDU size for the RACH are present.

If the criteria are met, the WTRU may select a preamble from the R99RACH fallback and may initiate a preamble ramp-up procedure. Based onthe selected preamble, the network may determine the preference and/ortype of WTRU performing uplink access and may determine the transportchannel to use. If the WTRU fails to meet the criteria, the WTRU mayselect a preamble from the common E-DCH preambles (e.g., legacy commonE-DCH preambles). In such instances, when the network receives thepreamble, the network may not know that the WTRU is R99 RACH capableand, therefore, may not have the option to send the WTRU to R99 RACH.

The WTRU's default resources may be the common E-DCH resources. The WTRUmay start using the common E-DCH resource associated with a defaultcommon E-DCH index, X, in response to receiving an ACK on the AICH. Forexample, X=Singlnd mod Y, where Singlnd may be the Nth preamble of theR99 fallback preamble list. The TTI configuration to use for the commonE-DCH may be the TTI configuration of the common E-DCH resources (e.g.,legacy common E-DCH resources) or, the common E-DCH may be provided tothe WTRU using any of the examples described herein. The EAI may be usedto signal the WTRU to fallback or use the R99 RACH by any of theimplementations described herein, such as but not limited to: a NACK onthe EAI; a reserved common E-DCH index; or a reserved value of EAI. Theother EAI values may be used to redirect the WTRU to use a differentcommon E-DCH resource index other than the default X. When no EAI isconfigured, a NACK on the AICH may signal such WTRUs to start using theR99 RACH.

The WTRU's default resources may be the R99 RACH resources. The WTRU maychoose a preamble from the R99 fallback RACH preambles. An ACK on theAICH may imply that the WTRU has been acknowledged to fallback or tostart using the R99 RACH. The NACK and/or EAI may be used to signal anindex to a common E-DCH according to any of the implementationsdescribed herein.

A WTRU may perform transport channel selection and may use a set ofreserved preambles to signal that it supports R99 RACH. For example, thepreambles may be reserved for R99 and/or they may be the preambles usedfor TTI selection (e.g., the preambles for 2 ms and/or 10 ms TTIconfiguration) that imply that the WTRU also supports R99 fallback. Thenetwork may not be aware of the WTRU buffer and/or RLC status. Thenetwork may still redirect the WTRU to use the R99 RACH according to anyof the implementations described herein. This may be applicable wherethe network is aware of the WTRU buffer and/or RLC status (e.g., thatthe criteria is not met), but the network still may have the option toredirect the WTRU to use R99 RACH. For example, if the criteria tofallback is dependent on the logical channel type, the WTRU may fallback(e.g., only fallback) if the uplink transmission belongs to thepredefined list and/or configured allowed channels (e.g., CCCH and/orDCCH may be part of the channel list). If the WTRU is R99 fallbackcapable, after performing a random access procedure trying to acquire acommon E-DCH resource, the WTRU may monitor the AICH and/or E-AI todetermine if a NACK on the AICH may be received. If the EAI value and/orcorresponding E-DCH resource index received is equivalent to the indexcorresponding to the fallback, and if there may be CCCH uplink data totransmit and CCCH fallback is allowed or if there may be DCCH uplinkdata to transmit and DCCH fallback is allowed, then the WTRU may performR99 RACH fallback. If the conditions above are not met (e.g., if thereis DTCH data to transmit), then the WTRU may not fallback to R99 RACH.Where the logical channel type allowed to fallback to R99 RACH is CCCH(e.g., only CCCH), then if the WTRU has DCCH or DTCH data fortransmission, the WTRU may determine not to fallback to R99 RACH. Uponreception of an indication to start using R99 RACH, the WTRU may startusing R99 RACH regardless of the buffer status and/or RLC status (e.g.,the WTRU may re-create the RLC PDUs or may create other RLC PDUs, forexample, in an attempt to transmit as much data as possible). The WTRUmay start using R99 RACH and, if the RLC status and/or buffer status arenot met, may use the RACH to transmit a TVM report. The WTRU may ignorethe network indication to fallback to R99 RACH, back off, and may try toaccess the UL again. For example, the WTRU may ignore the indicationfrom the network to fallback using a random access channel (e.g., R99RACH, R99 PRACH, etc.), may wait for a time (e.g., back off for apredetermined amount of time), and then may re-attempt to access thenetwork. When attempting the UL access, the WTRU may decide to choose apreamble from the common E-DCH resources (e.g., legacy common E-DCHresources), which may not allow the network to know that the WTRU may beR99 fallback capable. This may increase the chances of accessing the ULover the common E-DCH.

The WTRU may perform TTI selection based on one or more of the criteriadescribed herein (e.g., capability and power/headroom). Preambles (e.g.,new preambles) may be reserved to signal a TTI indication other than theTTI configuration signaled on the common E-DCH list (e.g., legacy commonE-DCH list). If the WTRU selects a TTI configuration other than the TTIused for the common E-DCH (e.g., legacy common E-DCH), then the WTRU maychose a preamble from the signaled PRACH resourced (e.g., new signaledPRACH resourced) for the TTI configuration (e.g., the new TTIconfiguration). The network may determine a preference of the WTRU. Thenetwork may become aware that the WTRU is TTI selection capable. Thenetwork may use any of the implementations described herein toacknowledge the selection or redirect the WTRU to a different TTI. Ifthe WTRU selects the same TTI as the TTI signaled on the common E-DCHresource (e.g., legacy common E-DCH resource), then the WTRU may pick apreamble from the common E-DCH PRACH resources (e.g., legacy commonE-DCH PRACH resources). The network may not know that this WTRU iscapable of TTI selection and may not redirect the WTRU to use any otherTTI. The AICH may be used according to the rules (e.g., the legacyrules) to indicate the common E-DCH index of the resources (e.g., legacyresources).

Preambles (e.g., new preambles) may be signaled for 2 ms TTI and 10 msTTI configurations (e.g., for WTRUs capable of TTI configuration). Basedon the chosen TTI, the WTRU may select the preamble from either the 2 msor the 10 ms group. The network may be aware of the preference and thatthe WTRU may be TTI selection capable. The network may use any of theimplementations described herein to redirect the WTRU.

Allowing a fallback to R99 RACH may result in transmissions of data overa R99 PRACH from a logical channel configured with flexible RLC PDUconfiguration. For example, considering that R99 RACH may not havesegmentation capabilities and may transmit a limited set of TBS, aflexible PDU RLC may coordinate the RLC PDU creation with the R99 RACHtransport format selection.

The RLC configuration in non-DCH states may correspond to flexible RLCPDU sizes. In order to enable transmission over R99 RACH, the RLC maycreate “radio aware RLC PDUs,” such that the RLC PDUs may be created tofit within a selected RACH TBS without MAC layer segmentation. Forexample, the WTRU may determine the RLC PDU size based on one or more ofthe following criteria. A criterion may be the selected TBS size. Acriterion may be the minimum selected TBS size and/or available numberof bits quantized to the lowest allowed TBS size that is equal to orsmaller than selected TBS. A criterion may be the minimum selected TBSsize, available number of bits, and/or available power quantized to thelowest allowed TBS size that is equal to or smaller than selected TBS.

If the WTRU performs delayed radio aware RLC PDU creation whenconfigured with fallback to R99 RACH and attempting a common E-DCHaccess, then the WTRU may start creating RLC PDUs after the E-DCHresource has been allocated to the WTRU. This procedure may prevent theWTRU from prematurely generating RLC PDUs that it may not be able totransmit over the R99 RACH. For example, the size of the delayed RLCPDUs might be decided according to any combination of the followingcriteria. A criterion may be the number of bits that may be transmittedaccording to, for example, the default grant broadcasted. A criterionmay be the minimum between number of bits that may be transmittedaccording to, for example, the default grant and/or an allowed TBS fromthe set of the R99 RACH transport formats. An allowed TBS may correspondto, for example, the smallest TBS and/or the largest TBS. A criterionmay be the minimum allowed TBS, available data, and/or default grantquantized to an allowed TBS size that may be smaller than the defaultgrant. The size of the delayed RLC PDUs may be decided based on abroadcasted RLC PDU size.

MAC segmentation may be allowed for transmission over R99 RACH. Forexample, the MAC-i/is sub-layer may segment RLC PDUs (or MAC-d PDUs)prior to delivery to the MAC-e sublayer for transmission over RACH. AMAC-i/is header may be included in the R99 RACH transmission in order toallow the Node B to reassemble the segments received across multiple R99RACH transmissions.

Upon a redirection/acknowledgement to R99 RACH, the WTRU may perform oneor more of the following. The WTRU may initiate a RACH preambletransmission procedure (e.g., a new RACH preamble transmissionprocedure) using the PRACH information of the R99 RACH resources (e.g.,legacy R99 RACH resources). This procedure may be accelerated using anyof the implementations described herein. The WTRU may initiate a PRACHmessage transmission upon reception of a redirection/acknowledgment touse R99 RACH (e.g., legacy R99 RACH). The timing to initiate the PRACHmessage transmission with respect to the AICH may be maintained. Forexample, the WTRU may use any combination of the following physicalchannel parameters to perform the PRACH message transmission: ascrambling code of the preamble selected from the R99 fallback PRACHresources; the signature sequence, s, of the preamble selected from theR99 fallback RACH resources and/or used to determine a channelizationcode; or the other physical channel parameters, transport channelformats, etc., that may be extracted from the PRACH information (e.g.,legacy PRACH information) (for example, if more than one PRACH info isselected, then the resources of the first one or a predefined one may beused). PRACH information (e.g., new PRACH information) may bebroadcasted to be used from such WTRUs.

After selection and/or redirection of the R99 RACH channel fortransmission, the WTRU may attempt to access the R99 RACH and/or mayperform UL transmission of data and/or control information. Uponcompletion of this procedure, wherein completion may refer totransmission of the data over the air interface or RACH failure, theWTRU may have data in its buffer. If the WTRU immediately performsaccess to common E-DCH again, the same congestion may still occur. Afterattempting E-DCH access, the WTRU may fail again and may perform anotherfallback to R99 RACH. This may result in access delays and/orping-ponging between different RACH accesses.

The behavior of the WTRU after a fallback to R99 RACH may be controlled.For example, a timer (e.g., a prohibit timer, a back-off timer, etc.)may be utilized to prevent the WTRU from attempting access on the commonE-DCH for a certain period of time. The timer may be started in one ormore of triggers. A trigger may be that the WTRU determines that afallback to R99 RACH has to be performed. A trigger may be that a R99RACH procedure has been completed as a result of a fallback to R99 RACH.A trigger may be that UL data was transmitted over the air using the R99RACH. If another UL access attempt has to be performed by the WTRU andthe timer is still running, then the WTRU may perform a R99 access. Ifthe timer is not running, the WTRU may access the common E-DCH and/orre-evaluate the criteria to choose which RACH resources to use. If thetimer is running and the WTRU has data to transmit, then the WTRU maytrigger a TVM report to the network, which may indicate the reason ofthe trigger.

The WTRU may fallback to R99 after a common E-DCH failure or directnetwork indication even if the criteria above are not met. A trafficvolume measurement (TVM) report may be triggered upon fallback to R99RACH. For example, a TVM may be triggered if the WTRU falls back to R99and various conditions are satisfied. A condition may be, for example,that the buffer size is above a threshold. This threshold may be afallback to R99 RACH specific threshold and/or may be smaller than thethreshold to trigger a TVM report for a WTRU using common E-DCH. Acondition may be, for example, that the logical channel with UL databelongs to a list of logical channels the WTRU may not be allowed to useR99 RACH, or to a list that may trigger a TVM report. For example, atleast two events may be configured for TVM reporting in the WTRU. Onemay be used when the WTRU is using common E-DCH and one may be used whenthe WTRU has performed a fallback to R99 RACH.

Faster RACH access may be provided where the WTRU may switch from aCommon E-DCH access attempt to a R99 RACH access attempt, and viceversa. These situations may include, without limitation, a WTRU fallingback to R99 RACH after having attempted common E-DCH access; a WTRUfalling back to R99 RACH after an explicit command from the networkafter having attempted to connect to a common E-DCH resource; and/or aWTRU performing access and potentially transmission on the R99 RACH anddetermining that more data remains in the buffer and then attemptingaccess to a common E-DCH resource.

In order to speed up such accesses, the WTRU may speed up the preamblephase, for example, by using a preamble power that is a function of thelast preamble power used on the previous resource (e.g., common E-DCHresource or R99 RACH resource). The preamble power may correspond to oneor more of the following. The preamble power may be the same power asthe last preamble transmitted on the other resources. The preamble powermay be the power of the last preamble transmitted on the other resourcesplus a configured offset.

The WTRU may speed up the access to the other resource by, for example,receiving a dedicated resource indication by the network. The resourceindication may include an index to a preamble signature of the set ofresources the WTRU is being signaled to access. In the case where aspecific signal may be used by the network to signal a fallback to R99RACH, this signal may include an index to a preamble resource (e.g., ascrambling code and/or a signature sequence, s, or index to PRACH info,if multiple PRACH info are signaled, that should be used by the WTRU).The index may be transmitted to the WTRU by means of an EAI. The signalmay indicate the resource index and/or the common E-DCH value to use.Implementations by which the WTRU may determine that the EAI may be usedto signal a UL channel selection (e.g., R99 RACH or TTI value) may bedescribed herein. For example, a secondary EAI may be used to signal anindex to a R99 PRACH preamble index and/or a common E-DCH resource indexfrom a group of resources corresponding to a TTI value and/or a preambleindex corresponding to a TTI value other than the requested value. Uponreception of this index, the WTRU may start the UL transmission on theindicated channel (e.g., RACH or common E-DCH with the indicated TTI).This may be performed with or without an acknowledgment required. TheWTRU may determine the power to use based on the last preambletransmission on the common E-DCH resource. The WTRU may start preambletransmission using the last used power on the other channel.

FIG. 2 illustrates an exemplary fallback. The method 200 of FIG. 2 maybe utilized by a WTRU to determine if it may fallback using a randomaccess channel (e.g., R99 RACH, R99 PRACH, etc.) to transmit uplinkinformation to a network. The WTRU may have uplink information such as,but not limited to, data or control information to transmit to anetwork. At step 201, a WTRU may request a common E-DCH resource fromthe network. For example, the WTRU's default resources may be the commonE-DCH resources.

After requesting a common E-DCH resource from the network, the WTRU mayreceive an indicator from the network to fallback to a random accesschannel (e.g., R99 RACH, R99 PRACH, etc.), thereby completing step 202.The indication may be received via an acquisition indicator (e.g.,E-AI). The indication may be a value of the E-AI. One or more E-AIvalues may be used to indicate the use of a random access channel (e.g.,R99 RACH, R99 PRACH, etc.) and one or more E-AI values may be used toindicate a common E-DCH index. For example, at least one value of theE-AI may be used to indicate that the WTRU may perform a fallback to arandom access channel (e.g., R99 RACH, R99 PRACH, etc.). The WTRU mayreceive the indication from the network to fallback regardless ofwhether or not the network is aware of the WTRU buffer and/or RLCstatus.

At step 203, the WTRU may determine if a condition is met. The conditionmay be met if one or more of the following is established: the channelfor transmission is capable of being mapped to the R99 RACH; the channelfor transmission may be configured with a fixed RLC PDU size; and/or thechannel for transmission belongs to a list of channels that ispredefined in the WTRU, whereby the list may include CCCH and/or DCCH.The condition may also be met if one or more of the conditions describedherein are established.

If the WTRU determines that the condition is met, then the WTRU mayfallback to the random access channel (e.g., R99 RACH, R99 PRACH, etc.)and may transmit the uplink information over the random access channel(e.g., R99 RACH, R99 PRACH, etc.), thereby completing step 204. Forexample, the WTRU may access the network with a PRACH R99 signature totransmit uplink information over the R99 RACH. The WTRU may initiate aRACH preamble transmission procedure using the PRACH information of theR99 RACH resource (e.g., legacy R99 RACH resources).

If the WTRU determines that the condition is not met, then the WTRU mayback off from accessing the network, thereby completing step 205. TheWTRU may determine that the condition is not met if one or more of theconditions described herein are not established. For example, the WTRUmay determine that the condition is not met if the channel fortransmission does not belong to the list of channels that is predefinedin the WTRU. The WTRU may ignore the indication from the network tofallback to the random access channel (e.g., R99 RACH, R99 PRACH, etc.).The WTRU may wait for a time (e.g., a predetermine amount of time)and/or may re-attempt to access the network.

The processes described above may be implemented in a computer program,software, and/or firmware incorporated in a computer-readable medium forexecution by a computer and/or processor. Examples of computer-readablemedia include, but are not limited to, electronic signals (transmittedover wired and/or wireless connections) and/or computer-readable storagemedia. Examples of computer-readable storage media include, but are notlimited to, a read only memory (ROM), a random access memory (RAM), aregister, cache memory, semiconductor memory devices, magnetic mediasuch as, but not limited to, internal hard disks and removable disks,magneto-optical media, and/or optical media such as CD-ROM disks, and/ordigital versatile disks (DVDs). A processor in association with softwaremay be used to implement a radio frequency transceiver for use in aWTRU, UE, terminal, base station, RNC, and/or any host computer.

What is claimed is:
 1. A method to transmit uplink information, themethod comprising: requesting, by a wireless transmit/receive unit(WTRU), a common enhanced dedicated channel (E-DCH) resource from anetwork; receiving an indication from the network to fallback to aRelease 99 Physical Random Access Channel (R99 PRACH); determiningwhether a condition is met, the condition being met if the WTRU has datato transmit on a channel configured for fallback to R99 PRACH; andtransmitting the uplink information over the R99 PRACH if the conditionis met and backing off from accessing the network when the condition isnot met.
 2. The method of claim 1, wherein the indication is receivedvia an acquisition indicator (E-AI).
 3. The method of claim 2, whereinthe indication is a value of the E-AI.
 4. The method of claim 1, whereinthe indication is an E-DCH resource index.
 5. The method of claim 1,wherein the uplink information is at least one of control information ordata.
 6. The method of claim 1, further comprising: receiving, from thenetwork, an information element (IE) that configures the channel forfallback to R99 PRACH.
 7. The method of claim 1, wherein the channelconfigured for fallback to R99 PRACH is a common control channel (CCCH)or a dedicated control channel (DCCH).
 8. The method of claim 1, whereinthe condition further comprises whether a Radio Link Control (RLC) sizeof the E-DCH is the same as a RLC size of the channel configured forfallback to R99 PRACH.
 9. The method of claim 1, wherein the WTRUutilizes a preamble indicating that the WTRU supports fallback to theR99 PRACH when requesting the common E-DCH resource from the network.10. The method of claim 1, wherein backing off comprises: ignoring theindication from the network to fallback to the R99 PRACH; waiting for atime; and attempting to access the network.
 11. A wirelesstransmit/receive unit (WTRU) configured to transmit uplink information,the WTRU comprising: a processor configured to: request a commonenhanced dedicated channel (E-DCH) resource from a network; anddetermine whether a condition is met, wherein the condition is met ifthe WTRU has data to transmit on a channel configured for fallback toR99 PRACH; and a transceiver configured to: receive an indication fromthe network to fallback to a Release 99 Physical Random Access Channel(R99 PRACH); and transmit the uplink information over the R99 PRACH ifthe condition is met and back off from accessing the network when thecondition is not met.
 12. The WTRU of claim 11, wherein the indicationis received via an acquisition indicator (E-AI).
 13. The WTRU of claim12, wherein the indication is a value of the E-AI.
 14. The WTRU of claim11, wherein the indication is an E-DCH resource index.
 15. The WTRU ofclaim 11, wherein the uplink information is at least one of controlinformation or data.
 16. The WTRU of claim 11, wherein the processor isfurther configured to receive, from the network, an information element(IE) that configures the channel for fallback to R99 PRACH.
 17. The WTRUof claim 11, wherein the channel configured for fallback to R99 PRACH isa common control channel (CCCH) or a dedicated control channel (DCCH).18. The WTRU of claim 11, wherein the condition further compriseswhether a Radio Link Control (RLC) size of the E-DCH is the same as aRLC size of the channel configured for fallback to R99 PRACH.
 19. TheWTRU of claim 11, wherein the processor is configured to request thecommon E-DCH resource from the network utilizing a preamble indicatingthat the WTRU supports fallback to the R99 PRACH.
 20. The WTRU of claim11, wherein backing off comprises: the processor further configured to:ignore the indication from the network to fallback to the R99 PRACH; andwait for a time; and the transceiver further configured to: attempt toaccess the network.